Have you ever walked past this building on rue la Fayette in the 10th arrondissement and wondered why the windows are always dark? The door is there, and the balconies look just like their neighbors, but they are hiding something unusual behind them. It turns out the façade is only a front with no building behind it. According to the blog Paris by Cell Phone, 145 rue la Fayette is a fake building hiding a ventilation chimney for the métro, much like the fake brownstone in Brooklyn that conceals an MTA subway ventilator.